1. Field of the Invention
This invention relates to the structure of a CRT (Cathode-Ray-Tube) socket for connecting a cathode ray tube used in a color television, etc., and particularly relates to a resistance element connecting structure ofthe CRT socket in which a resistance element is connected in series with a focus contact.
2. Description of the Background Art
In a CRT socket for connection to a cathode ray tube, an undesired radiating signal is generated by a high frequency signal applied to a cathode ofthe cathode ray tube through a focus circuit block. The high frequency signal influences the focus of an electronic beam. A terminal connected to a flyback transformer is attached to the CRT socket. Conventionally, a resistance element is connected in series between this terminal and a focus contact in the interior of the CRT socket to reduce the above influence.
The resistance element can be connected by directly soldering lead portions on both sides of the resistance element to the terminal and the focus contact. However, it is very difficult to make a soldering connecting work within a housing of the CRT socket, wherein the CRT socket is made as compact as possible.
Referring now to FIGS. 11-13, conventionally, a resistance element connecting structure 100 of the CRT socket connects both side lead portions of the resistance element in press contact with press contact slits concavely arranged in the terminal and the focus contact. A CRT socket 101 is assembled by attaching parts, to be described later, to a housing main body 102 from the rear. The housing main body 102 is formed by integrally molding a cylindrical housing 102a on one side (a lower side in FIG. 11) and a generally box-shaped housing 102b on the other side. A bottom face side of the box-shaped housing 102b has an open face to enable attachment of the constructional parts. After all ofthe parts are installed, the open face of the box-shaped housing 102b is covered with a bottom cover 102c. 
The cathode ray tube is connected to a planar side of the cylindrical housing 102a. The cathode ray tube is attached from a bottom face side of the cylindrical housing 102a in contact with pins of a neck portion of the cathode ray tube such that plural contacts 104 are located on the same circular circumference on this plane side.
A contact 104F in FIG. 11 among these contacts 104 is a focus contact to which a high voltage is particularly applied in comparison with the other contacts 104. A connecting portion 105 at one end of this focus contact is pulled out into the lower measure type housing 102b to reliably insulate the focus contact from the other contacts 104.
As shown in FIG. 13, an end portion of the connecting portion 105 is bent in a downward U-shape. Two parallel press contact slits 106 are concavely formed in the bent portion. A connecting piece 107a of a focus side discharge electrode plate 107 is press-fitted into one press contact slit 106. The press contact slit 106 is electrically connected to the focus side discharge electrode plate 107. The focus side discharge electrode plate 107 has a center of the focus side discharge electrode plate 107 projecting in a spherical or conical shape.
The focus side discharge electrode plate 107 is attached to a side wall surrounding a discharge air gap chamber 108 formed within the box-shaped housing 102b (see FIG. 12). The focus side discharge electrode plate 107 is positioned opposite to a ground side discharge electrode plate 109 similarly formed such that the focus side discharge electrode plate 107 and the ground side discharge electrode plate 109 form a discharge gap within the discharge air gap chamber 108. This discharge gap remains quiescent while a normal voltage is applied to the focus contact 104F. When a discharge occurs within the cathode ray tube, the discharge gap discharges spark energy of this discharge to the ground side discharge electrode plate 109 to prevent discharged electric current from flowing in the reverse direction from the focus contact 104F to a semiconductor element within a circuit.
In FIG. 12, a terminal storing concave portion 111 is concavely arranged from an open face 103 on a side partitioned by a partition wall 110 from the discharge air gap chamber 108 within the box-shaped housing 102b. A terminal 112 is stored to the terminal storing concave portion 111. In the terminal 112, an external connecting portion 112a and a resistance connecting portion 112b are continuously integrated with each other. A portion of the terminal storing concave portion 111 for storing the external connecting portion 112a extends through a plane side of the box-shaped housing 102b. One end of an external lead wire 114, having its other end connected to a flyback transformer, is inserted from the plane side into this through hole where it comes into elastic contact with an elastic contact piece 112c of the external connecting portion 112a. 
Similar to the end portion of the connecting portion 105, as shown in FIG. 13, the resistance connecting portion 112b is bent in a downward U-shape. A press contact slit 116 is concavely formed in this bent portion. Both side lead portions 115a of the resistance element 115 are respectively press-fitted into press contact slits 116, 106 of end portions of this resistance connecting portion 112b and the connecting portion 105 from the open face 103 of the box-shaped housing 102b. Thus, the resistance element 115 is connected in series between the focus contact 104F and the flyback transformer.
In this connecting work, it is sufficient to press-fit both end lead portions 115a of the resistance element 115 to the press contact slits 116, 106 respectively formed in the terminal 112. The connecting portion 105 of the focus contact after the terminal 112 and the focus contact 104F are attached into the box-shaped housing 102b. Accordingly, soldering is not required. Therefore, the connection is easily made.
However, it is desirable to make the CRT socket in a shape that is as compact as possible in order to accomplish high density mounting. But the conventional resistance element connecting structure 100 positions the resistance element 115 parallel to the open face 103 of the box-shaped housing 102b. Therefore, the space required for the resistance element 115 is enlarged in a plane direction of the box-shaped housing 102b and thereby interferes with the desire to make the CRT socket 101 compact.
Therefore, as shown in FIG. 14, a resistance element connecting structure 120 for storing the resistance element 115 in a vertical direction with respect to a box-shaped housing 121 has also been developed. In this resistance element connecting structure 120, both end lead portions 115a of the resistance element 115 are press-fitted into press contact slits 124, 124 formed in a terminal 122. A connecting portion 123 is connected to an unillustrated focus contact. The resistance element 115 is stored toward a side of a terminal storing concave portion 125 along an attaching direction of the terminal 122.
However, in this resistance element connecting structure 120, the resistance element 115 is attached after the terminal 122 and the focus contact are attached from an open plane side (an upper side in FIG. 14) of the box-shaped housing 121. Therefore, the lead portions 115a of the resistance element 115 are press-fitted to the press contact slits 124, 124 of the terminal 122 and the connecting portion 123 from the open plane side (the upper side) using a jig. Accordingly, there is no storing space for the resistance element 115 on an inner side (lower side) onto which the terminal 122 or the focus contact is attached. Therefore, the only available storing space is located in a space between the terminal 122 and the focus contact. As a result, the CRT socket is inevitably larger to permit installation of the resistance element 115.
Further, the positioning of the resistance element 115 in the vertical direction requires that press contact slits 124, 124 on sides of the terminal 122 and the focus contact are close together. Therefore, it is difficult to press-fit the bent lead portions 115a. Further, one lead portion 115a of the resistance element 115 on a side connected to the connecting portion 123 must be pulled out on the inner side (lower side). Therefore, it is necessary to arrange a lead portion having an excessive length.
To solve the above problems, an object of this invention is to provide a resistance element connecting structure of a CRT socket in which a resistance element can be connected simply work, and which does not require an increase in the size of the CRT socket for connection of a resistor.
To solve the above problems, a resistance element connecting structure of a CRT socket according to the invention comprises a focus contact connected to a focus pin of a cathode ray tube; a terminal connected to an external lead wire; a focus side discharge electrode plate connected to the focus contact; a ground side discharge electrode plate; and a box-shaped housing in which a contact storing concave portion for storing the focus contact, a terminal storing concave portion for storing the terminal, and a discharge air gap chamber for oppositely arranging the focus side discharge electrode plate and the ground side discharge electrode plate spaced from each other by a discharge gap are concavely arranged from an open face on one side of the box-shaped housing; wherein a resistance element is connected in series between the focus contact attached from the open face to the contact storing concave portion and the terminal attached from the open face to the terminal storing concave portion; the focus side discharge electrode plate is formed by a metallic plate in which a spherical electrode portion is projected at a center of the metallic plate, and an elastic contact piece is projected from a bottom edge of the metallic plate in a direction reverse to a projecting direction of the electrode portion; an attaching frame portion for nipping and fixing both sides of the focus side discharge electrode plate is formed in a side wall surrounding the discharge air gap chamber of the box-shaped housing; an inside lead portion of the resistance element having an outside lead portion connected to the terminal is arranged outside the side wall; the bottom edge of the metallic plate is directed toward the interior of the box-shaped housing, and the focus side discharge electrode plate is attached to the attaching frame portion from the open face along the side wall, and the electrode portion of the focus side discharge electrode plate faces the discharge air gap chamber, and the elastic contact piece projected to an outer side from the side wall of the discharge air gap chamber comes in elastic contact with the inside lead portion of the resistance element; and the focus side discharge electrode plate connected to the focus contact is connected to the inside lead portion of the resistance element.
The elastic contact piece is projected to the bottom edge of the focus side discharge electrode plate, and this focus side discharge electrode plate is attached to the attaching frame portion. Thus, the electrode portion of the focus side discharge electrode plate faces the discharge air gap chamber, and the elastic contact piece comes in elastic contact with the inside lead portion ofthe resistance element. Accordingly, the inside lead portion of the resistance element can be electrically connected to the focus contact only by attaching the focus side discharge electrode plate connected to the focus contact.
The resistance element can be also stored into the box-shaped housing together with the attachment of the terminal. Accordingly, the outside lead portion of the resistance element can be connected to the terminal in advance before the terminal is attached to the box-shaped housing. Therefore, the outside lead portion can be easily connected and can be also connected by soldering.
A resistance element connecting structure ofthe CRT socket according to a further aspect of the invention includes a terminal that has an external connecting portion connected to the external lead wire, and a resistance connecting portion integrally and continuously arranged on a side of the external connecting portion; a resistance storing portion is continuously arranged inward along an attaching direction of the terminal from a portion of the terminal storing concave portion storing the resistance connecting portion therein; and the resistance element having the outside lead portion connected to the terminal is stored to the resistance storing portion.
It is not necessary to connect the resistance element after the terminal is attached to the box-shaped housing. Therefore, the resistance storing portion can be continuously arranged inside the terminal storing concave portion along an attaching direction of the terminal, and the resistance element can be stored to the resistance storing portion. Accordingly, the compactness of the CRT socket remains unrestricted by need to provide a storing space for the resistance element.
A resistance element connecting structure of the CRT socket in claim 3 is characterized in that the focus contact and the focus side discharge electrode plate are integrally molded by punching the metallic plate.
Since the focus contact and the focus side discharge electrode plate are integrally molded, the number of parts is not increased. Further, the inside lead portion of the resistance element can be electrically connected to the focus contact by one attaching work for attaching the focus contact and the focus side discharge electrode plate.